The present invention relates to a pump assembly which has a container for storing a liquid such as a chemical solution in isolation from ambient air so that the stored liquid will be protected from being modified, e.g., oxidized, and which can discharge the stored liquid from the container while the liquid is being isolated from ambient air.
One known pump assembly is shown in FIG. 5 of the accompanying drawings.
The pump assembly shown in FIG. 5 comprises a substantially cylindrical container a with open opposite ends, a pump b mounted in the upper end of the container a, and a gasket c slidably inserted in the other bottom end of the container a. With the pump b mounted in the upper end of the container a, a liquid X such as a chemical solution is filled in the container a through the bottom end thereof, and thereafter the gasket c is inserted into the container a until the gasket c contacts the surface of the liquid X. The liquid X is now sealed in the container a in isolation from ambient air. After the liquid X is sealed in the container a, the bottom end of the container a is closed by an air-permeable bottom lid d.
The pump b may be a pump disclosed in Japanese Laid-Open Patent Publication No. 61(1986)-263668, for example. When a presser e of the pump b is pressed by a finger, the pump b draws in the liquid X from the container a through a suction port f and ejects the liquid X from an outlet port g. The suction port f of the pump b which is installed in the upper end of the container a extends through a neck h on the upper end thereof and is immersed in the liquid X.
When the liquid X in the container a is drawn and ejected out of the container a by the pump b, the gasket c slides toward the pump b while in contact with the surface of the liquid X as the amount of the stored liquid X is progressively reduced. Therefore, the liquid X stored in the container a remains sealed, i.e., in isolation from the ambient air, and is prevented from being modified, e.g., oxidized by contact with the ambient air.
While the liquid X sealed in the container a remains isolated from the ambient air, air often tends to flow into the container a when the liquid X is introduced into the container a. The air Y, which enters into the container a when the liquid X is filled, is trapped between the suction port f of the pump b and the neck h, and cannot easily be removed from the container a after the liquid X has been sealed in the container a.
Therefore, the liquid X in the container a may be oxidized by the trapped air Y. To prevent such oxidization of the liquid X, it has been necessary to replace the air X with a nitrogen gas when the liquid X is sealed. Such a replacing procedure is however tedious and time-consuming.